Hydraulic system

ABSTRACT

A hydraulic system includes a master cylinder having a housing, a piston axially movably disposed in the housing, and a piston rod, the piston bounding a pressure chamber filled with a hydraulic fluid, the piston upon actuation of the master cylinder being axially moved by the piston rod to pressurize the hydraulic fluid; an actuating device for moving the piston rod; a slave cylinder; a pressure-medium line connecting the master cylinder and slave cylinder; and at least one damping element arranged between the actuating device and the slave cylinder.

This is a divisional of U.S. patent Ser. No. 10/705,050, filed Nov. 10,2003, which claims priority to German Patent Application No. 102 52408.4, filed Nov. 12, 2002, which is hereby incorporated by referenceherein.

BACKGROUND INFORMATION

The present invention relates to a hydraulic system, in particular formotor vehicles, including a master cylinder having a housing, a pistonwhich is axially movably disposed therein, which bounds a pressurechamber filled with a hydraulic fluid, and which, upon actuation of themaster cylinder, is axially moved by a piston rod acting upon thepiston, thereby pressurizing the hydraulic fluid; the system furtherincluding a slave cylinder and a pressure-medium line connecting thecylinders, the master cylinder haying an adapter for detachableconnection to the pressure-medium line.

A hydraulic system of this type is known, for example, from GermanPatent Application No. 100 49 913 A1, which is related to U.S. Pat. No.6,446,436. Both of these documents are hereby incorporated by referenceherein

In a prior art hydraulic system, the connection between the adapter andthe pressure-medium line is problematic. If plastic is used for theadapter, leaks can occur, or a high assembly force may be required.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention to improve the connection between thepressure-medium line and the adapter.

The present invention provides a hydraulic system, in particular formotor vehicles, that includes a master cylinder having a housing, apiston which is axially movably disposed therein, which bounds apressure chamber filled with a hydraulic fluid, and which, uponactuation of the master cylinder, is axially moved by a piston rodacting upon the piston, thereby pressurizing the hydraulic fluid. Thesystem further includes a slave cylinder and a pressure-medium lineconnecting the cylinders, the master cylinder having an adapter fordetachable connection to the pressure-medium line. The adapter includesa sleeve made of a metal.

In this context, the sleeve can be manufactured from brass, aluminum,steel, or the like. The sleeve can be produced by turning, punching,deep drawing, or other known manufacturing processes. In this context,“sleeve” is understood to mean any type of insert on the inner side of abore or the like.

In an advantageous embodiment, the sleeve may have, at least partially,a polygonal outer cross-section which fixes the sleeve against rotationin a bore of a housing flange. In this context, a “polygonalcross-section” is understood to include, for example, also an ellipticalcross-section or a cross-section having rounded corners. In thisconnection, the corresponding housing opening or bore can already bemade to match the outer contour of the sleeve. Alternatively, forexample, circular bores or stepped bores are also possible, the sleevebeing pressed into the circular or stepped bore so that the polygonalinner cross-section of bores is formed only by pressing-in the sleeve.The housing flange can be located at any point on the master cylinder.For example, it can also be located within the imaginary extension ofthe piston. The polygonal outer cross-section of the sleeve may preventrotation of the sleeve about its longitudinal axis due to acorresponding inner cross-section of the bore of the housing flange.Preferably, the inner cross-section of the sleeve has a circular shapematching the outer cross-section of a corresponding connector of thepressure-medium line. The connection between the sleeve and theconnector of the pressure-medium line can be secured in known manner bya clamp or the like.

In a further advantageous embodiment, provision may be made for thesleeve to have a first region and a second region with at least thefirst region and/or the second region having a polygonal outercross-section. The adapter then may have a stepped bore including afirst step corresponding to the first region, and a second stepcorresponding to the second region. Thus, the sleeve has a polygonalcross-section only over part of its depth. The polygonal cross-sectioncan also be provided in the form of a knurling near the upper or lowerside of the sleeve. It is advantageous if the second region has asmaller diameter than the first region because the associated sealcross-sections can thus be minimized.

In a further advantageous embodiment, the stepped bore may have, atleast partially, a polygonal bore cross-section. In another advantageousembodiment, the first region may have a polygonal outer cross-sectionand the second region may have an essentially round outer cross-section.Thus, a fit between two circular sections that is quite easy to seal canbe obtained in the region of smaller diameter.

In another alternative embodiment, the first region may have anessentially round outer cross-section and the second region may have apolygonal outer cross-section.

In a further advantageous embodiment, provision may be made for thesleeve to be sealed from the environment by an annular seal. In thiscontext, the annular seal can be located in a circumferential annulargroove of the sleeve. The annular seal can be a conventional O-ring, aseal having, for example, a trapezoidal oval cross-section. The seal ispreferably circumferential in design.

In another advantageous embodiment, provision may be made for theadapter to be located laterally on the housing. Thus, it is possible toreduce the overall length of the master cylinder.

In a further advantageous embodiment, the sleeve may be fixedly and/ordetachably connected to the housing. Therefore, the sleeve can, forexample, be pressed in or glued in. Alternatively or additionally,provision may be made for undercuts which retain the sleeve in themanner of a clip connection.

Moreover, in a hydraulic system according to the prior art mentioned atthe outset, the problem arises that pressure vibrations within thehydraulic system are directly transmitted, for example, to an actuatingpedal.

It is therefore an alternate or additional object of the presentinvention to provide a hydraulic system in which pressure vibrationswithin the hydraulic system are not, or only to a lesser extent,transmitted to an actuating element such as an actuator, or a clutchpedal, or the like.

The present invention also provides a hydraulic system, in particularfor motor vehicles, that includes a master cylinder having a housing, apiston which is axially movably disposed therein, which bounds apressure chamber filled with a hydraulic fluid, and which, uponactuation of the master cylinder, is axially moved by a piston rodacting upon the piston, thereby pressurizing the hydraulic fluid. Thesystem further includes a slave cylinder and a pressure-medium lineconnecting the cylinders, in which hydraulic system at least one dampingelement is located between the actuating device and the slave cylinder.The damping element can be any type of coupling element which allowsvibrational isolation or which allows damping of transmitted vibrations.

In an advantageous embodiment, provision may be made for the piston rodto include a damping element located directly at a connecting piece. Theconnecting piece connects the piston rod to an actuating element, suchas an actuator or a clutch or brake pedal. By arranging the dampingelement directly at the connecting piece, it is possible to minimize therequired length of the piston rod.

In another advantageous embodiment, provision may be made for thedamping element to include a first damper element, which is connected tothe connecting piece, as well as a second damper element, which isconnected to the piston rod. In this context, it is particularlyadvantageous if the first damper element and/or the second damperelement is/are made of plastic. Manufacture from plastic of the damperelements typically is more cost-effective than manufacturing suchcomponents from metal, and, in addition, the mass of the damping elementtypically may be reduced.

In a further advantageous embodiment, the damping element may include adamping cushion, and that the first damper element is axially movablerelative to the second damper element against the damping cushion. Thedamping cushion may be composed of a highly damping material, preferablyof a rubber-elastic material. Thus, the first and second damper elementsform a kind of a movable housing which accommodates the damping cushion.

In another advantageous embodiment, provision may be made for the firstdamper element to include a first region encompassing the dampingcushion, and a second region supporting the connecting piece. Thus, thefirst damper element is divided into two functional regions. The firstregion advantageously may have a cup-like shape.

In a further advantageous embodiment, provision may be made for thepiston rod to have a pin which extends at least partially into a bore ofthe second region. The pin serves to mechanically stabilize the secondregion. This is important especially if the second region is made ofplastic because when the master cylinder is actuated through the pistonrod, and thus also through the damper element and the connecting piece,bending forces and, in particular, buckling forces resulting from thecompressive force have to be transmitted, which could overload theconnecting piece if it is manufactured from plastic. Thus, the flexuralstiffness and, in particular, the buckling strength of the componentsthat are made of plastic are increased to such an extent that the riskof failure due to kinking, shearing off, or the like, is reduced.

In another advantageous embodiment, provision may be made for the pin tobe arranged in the bore in such a manner that it can move in an axialdirection. Therefore, the pin does not hinder the damping function.

In a further advantageous embodiment of the present invention, thedamping element may be located in the pressure-medium line between themaster cylinder and the slave cylinder. Thus, pressure vibrations can bedamped before they reach the master cylinder.

The damping element may be advantageously configured as a disk, it alsobeing possible to arrange a plurality of such disks behind one anotherto increase the damping effect in this manner. This may be achieved inthat the disk is provided at its front side with a spline reaching fromoutside to a predefined inner diameter, and in that the surface of thedisk is provided with a plurality of annular grooves to form ridges,these ridges alternately ending at the spline or being spaced aparttherefrom. In this manner, the hydraulic fluid is positively guidedthrough the grooves, the guiding direction being reversed at the ends ofthe ridges.

A bore provided in the outermost groove of the disk and connected to thepressure line allows the hydraulic fluid to enter the damping element.The exit of the hydraulic fluid is via the bore that is located at theend of the circular groove and also connected to a pressure-medium line.

In place of a plurality of disks arranged one behind the other, dampingcan also be accomplished by a labyrinth body in order to achieve optimumdamping of the pressure vibrations. The labyrinth body may be composedof a cylindrical housing in which is located a cylinder provided withbores extending in an axial direction. The cylinder then may be sealedagainst the surrounding housing with seals, the housing being closablewith a cover. The cover and the cylinder are provided with suitablebores allowing connection to the pressure lines.

Advantageously, in each case two bores in the cylinder may be connectedalternately at the end faces. The remaining ridges form a part of acircular arc and are predominantly arranged circularly. In this context,the hydraulic fluid is positively guided within the cylinder, just as inthe case of the disk. Due to the multitude of paths created in thismanner, the hydraulic fluid, which is acted upon by pressure vibrations,is damped over the path from the inlet to the outlet of the cylinder. Inthis context, the size of the labyrinth body can be adapted, on the onehand, to the structural conditions in the vehicle space and, on theother hand, to the magnitude of the pressure vibrations.

A further advantage is that the two damping elements, the disk and thelabyrinth body, can be made of plastic, metallic or nonmetallicmaterial.

In a further embodiment of the present invention, the damping elementmay be composed of a combination of a pulsation filter and at least onethrottle. This has the advantage that the vibration-carrying fluid flowcan be controlled as a function of pressure. Thus, the fluid flow caneither pass only through the throttle or, additionally, through thepulsation filter.

In order to increase the hydraulic stiffness of the master cylinder, itis known to manufacture the pressure chamber from metal, for example, inthe form of a cylinder sleeve inserted into the plastic housing. In thiscontext, it is problematic to fix the cylinder sleeve in position.

Another alternate or additional object of the present invention toprovide a hydraulic system of the type mentioned at the outset, in whichthe cylinder sleeve is fixed in position more effectively.

The present invention provides a hydraulic system, in particular formotor vehicles, that includes a master cylinder having a housing, apiston which is axially movably disposed therein, which bounds apressure chamber filled with a hydraulic fluid, and which, uponactuation of the master cylinder, is axially moved by a piston rodacting upon the piston, thereby pressurizing the hydraulic fluid. Thesystem further includes a slave cylinder and a pressure-medium lineconnecting the cylinders, in which hydraulic system the master cylinderincludes a replenishing nozzle which, on the side facing the piston inthe installed position, has a projection which reaches behind a cylindersleeve in the radial direction thereof. Thus, the cylinder sleeve canonly be pulled out when the replenishing nozzle is not mounted. This isimportant especially when it is necessary to transport a partiallyassembled housing. When the replenishing nozzle is mounted immediatelyafter mounting the cylinder sleeve, then the position of the cylindersleeve can no longer be changed in an axial direction, even if thepiston and the weld ring are not installed. However, a change inposition in an axial direction is therefore not possible in a completelyassembled condition either. Thus, the projection also serves to fix thecylinder sleeve in the installed position, that is, when the mastercylinder is completely assembled. Therefore, no further measures arerequired to fix the cylinder sleeve in the axial direction.

In a further advantageous embodiment, provision may be made for thecylinder sleeve to include a radially enlarged collar. In this context,it is particularly advantageous if the projection extends to the insidediameter of the collar in a radial direction with respect to the axis ofrotation of the piston, leaving a gap between the piston and theprojection. Thus, direct contact of the projection with the piston isprevented even in the case of large manufacturing tolerances of theprojection.

In another advantageous embodiment, provision may be made for thecylinder sleeve to be asymmetrical in shape at least at its front end.For this purpose, the cylinder sleeve can have a nose at its front end,the nose engaging in a corresponding recess of the housing.

An asymmetrical design can be achieved, for example, with a shapesimilar to a tube that is cut at an angle. In this context, it is onlyimportant that the cylinder sleeve have a shape which, together with amatching recess of the housing, prevents rotation of the cylinder sleeveabout the longitudinal axis. The anti-rotation feature ensures thatbreather ports or breather grooves or the like provided in the cylindersleeve are not changed in position with respect to a replenishingchamber or nozzle. Thus, the breather ports remain in the region of thereplenishing chamber or replenishing nozzle and cannot be rotatedrelative thereto.

In a further advantageous embodiment, the position of the projectionwith respect to the longitudinal axis of the slip socket may be on theside of the slip socket facing away from the pressure chamber. In otherwords, the cylinder sleeve completely covers the replenishing port sothat the breather clearance can be determined by the cylinder sleeve andthe length thereof or the arrangement of the breather ports or breathergrooves.

The aforementioned objects may be achieved by a master cylinder havingone of the above features relating to the master cylinder, and by ahydraulic system having one of the features described in the presentspecification.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention are described in moredetail below with reference to the accompanying drawings, in which

FIG. 1 is a schematic representation of a hydraulic system based on anexemplary embodiment of a clutch release device;

FIG. 2 is a longitudinal section of a master cylinder in a firstposition;

FIG. 3 is a longitudinal section of the master cylinder of FIG. 2 in asecond position;

FIG. 4 shows the master cylinder in a three-dimensional representation;

FIG. 5 is end view toward line A-A in FIG. 3;

FIG. 6 shows an enlarged detail of the replenishing nozzle of FIG. 2;

FIG. 7 shows an enlarged detail of the front region of the mastercylinder of FIG. 2;

FIG. 8 shows an embodiment of a damping device in the form of a disk;

FIG. 9 is a section through the damping device according to FIG. 8;

FIG. 10 shows an embodiment of a damping device in the form of alabyrinth body;

FIG. 11 is a section through the damping device according to FIG. 10;

FIG. 12 is a schematic representation of an embodiment of a dampingdevice as a combination of a pulsation filter and a throttle;

FIG. 13 shows oil flow passageways through the damping device accordingto FIG. 12.

DETAILED DESCRIPTION

In FIG. 1, a possible embodiment of a hydraulic system having apressure-limiting valve or damping element 2 is schematically shownthrough a clutch release device 3 including a master cylinder 4 and aslave cylinder 5. In the exemplary embodiment shown, pressure-limitingvalve 2 is installed in line sections 11 and 12, separating them fromeach other in an unopened condition. It is to be understood that inother exemplary embodiments, pressure-limiting valve 2 can be integratedinto master cylinder 4 or into slave cylinder 5, and in other hydraulicsystems, such as brake systems, power steering systems, and the like, itcan be integrated into a functional component. Furthermore, apressure-limiting valve according to the present invention can be usedin an advantageous manner in any hydraulic line system as apressure-limiting valve and/or as a vibration filter, such as aso-called “pulsation filter”.

Clutch release system 3 hydraulically operates clutch 7 by acting uponmaster cylinder 4 through an actuating member 14, which can be a footpedal, an actuator such as an electric actuator, or the like. In thismanner, pressure is built up in master cylinder 4 by a mechanicaltransmission device 13. Master cylinder 4 builds up pressure in slavecylinder 5 via line section 12, pressure-limiting valve 2, and linesection 11. Slave cylinder 5 can be arranged concentrically around atransmission input shaft 10 and be axially supported on a transmissionhousing, and is able to apply the necessary release force to clutch 7via a release bearing, or to the release elements of the clutch, such asthe disk spring. As shown in FIG. 1, further embodiments can provide fora slave cylinder 5, which actuates a disengagement element via adisengagement mechanism 6, and which is located outside the clutch bell.The slave cylinder 5 acts upon the disengagement mechanism 6 in an axialdirection using a piston which is in hydraulic communication with themaster cylinder 4 and accommodated in the slave cylinder housing. Toapply the release force, the slave cylinder 5 may be immovably securedto the transmission housing, or to another component that is immovablerelative to the housing. When clutch 7 is closed, transmission inputshaft 10 transmits the torque of internal combustion engine 8 to atransmission, and then to the drive wheels of a motor vehicle.

Crankshaft 9 experiences irregular loading as a result of the combustionprocesses in internal combustion engine 8 and as a function of thedesign of internal combustion engine 8, depending, for example, on thenumber of cylinders. The irregular loads are manifested as axial and/orwobbling vibrations and are transmitted through disengagement mechanism6 to slave cylinder 5, and through line system 11, 12, to mastercylinder 4, and from there through mechanical transmission device 13 toactuating member 14. If the actuating member is a clutch pedal, thesevibrations are perceived as an annoyance. In case the actuating member14 is an actuator, such vibrations can result in, for example, reducedcontrol accuracy, or a shortened service life. Pressure-limiting valve 2is therefore inserted in lines 11, 12 for damping purposes, and tuned todamp the vibrations introduced by crankshaft 9. Such vibrationstypically fall in the frequency range of 50 to 200 Hz.

FIG. 2 is a longitudinal section of a master cylinder 4 in a firstposition. Master cylinder 4 includes a housing 15 and a piston 16 whichis axially movably disposed therein. In FIG. 2, the axial direction isdefined by a double arrow 17. Piston 16 includes a piston body, which isusually made of plastic, for example, by injection molding or the like,and which may include a piston sleeve, which substantially surrounds thepiston body at its periphery and which can be made of a metal. In thepresent exemplary embodiment, piston 16 is made completely of plastic.The substantially cylindrical piston 16 is located in a cylinder bore 18within housing 15. Piston 16, together with housing 15 or cylinder bore18, forms a pressure chamber 19. Piston 16 has an extension 20, whichmay be substantially cylindrical in shape and arranged coaxially withthe piston, and which extends from a piston crown 21 in the direction ofpressure chamber 19. Pressure chamber 19 is enlarged by an auxiliarychamber 22 on the side facing piston 16. A biasing spring 24 is arrangedbetween a bottom 23 of auxiliary chamber 22 and piston crown 21. Theinside diameter of auxiliary chamber 22 is reduced in the region ofbottom 23 and is approximately equal to the outside diameter of biasingspring 24. The spring retainer 25 formed in this manner secures spring24 both axially and against rotation. The inside diameter of theremaining region of auxiliary chamber 22 is slightly greater than theoutside diameter of spring 24, both in the unloaded and loaded conditionof spring 24. In the region of piston crown 21, extension 20 hasenlarged portions 26 which prevent excessive radial play of biasingspring 24 with respect to extension 20. Extension 20, first of all,serves to guide biasing spring 24 and prevents kinking or the likeduring compression of spring 24; secondly, the extension reduces thetotal volume of pressure chamber 19. The length of pressure chamber 19,in conjunction with auxiliary chamber 22, is a function of the desiredspring force and the desired characteristic of the spring force.Therefore, the length of biasing spring 24 cannot be shortenedarbitrarily. The volume of auxiliary chamber 22, which is per se almostirrelevant to the function of the master cylinder, is compensated inthis way.

As seen in FIG. 7, cylinder sleeve 57 is asymmetrical in shape at itsfront end 85 facing auxiliary chamber 22, and has a nose 86 projectingbeyond end face 88 of cylinder sleeve 57 by an overlength 87. The shapeof the inner contour of housing 15 is matched to the outer contour ofsleeve 57 so that nose 86 engages, for example, in a correspondingrecess of housing 15. Nose 86 prevents rotation of the cylinder sleeve57 about its longitudinal axis. A seal 89 seals cylinder sleeve 57against housing 15. Cylinder sleeve 57 must be secured against rotationto ensure the correct position of breather port 90 or the breathergrooves integrated therein with respect to replenishing chamber 65.

Piston 16 has a circumferential annular groove 27 which is locatedimmediately behind piston crown 21 and accommodates a substantiallycircumferential primary seal 28. Primary seal 28 serves to seal piston16 against cylinder bore 18 when piston 16 is actuated. In a rear region29 of piston 16, as shown in FIG. 2, a piston rod 30 is supported by aspherical segment 31. Spherical segment 31 is formed by a sphericalrecess 32 which extends toward a rear edge 33 of piston 16 in the formof a widening truncated cone 34. The mating part of spherical recess 32is a ball head 35 of piston rod 30. Piston rod 30 also has a stop disk36 which, when in the installed position, is only slightly spaced fromrear edge 33. The clearance is selected in such a manner that piston rod30 can be slightly rotated in the drawing plane of FIG. 2, orperpendicularly to the drawing plane of FIG. 2, as far as allowed bytruncated cone 34 without stop disk 36 touching rear edge 33 of piston16. In the rear position, which is shown in FIG. 2, stop disk 36 hits astop 37 which is fixedly connected to housing 15, thus preventing piston16 from being completely pulled out.

Piston rod 30 also includes a damping element 38. Damping element 38 isconnected to a connecting piece 39 which, in the case of manualactuation, is directly connected to a clutch or brake pedal.

The following is a more detailed description of the construction ofdamping element 38. The damping element 38 includes a first damperelement 40 composed of a cup-shaped first region 41 and a substantiallycylindrical second region 42. Connecting piece 39 is supported by thesecond region 42; first region 41, second region 42, and connectingpiece 39 being integrally formed of, for example, plastic.Alternatively, these individual parts can also be manufacturedseparately, and be detachably or permanently connected to each other,for example, by bonding, or welding, or screwing. Damping element 38also includes a second damper element 43, which is composed of asubstantially disk-shaped region 44 and a receiving flange 45. Seconddamper element 43 can be made, for example, of plastic by injectionmolding or of metal, and be manufactured in one piece, for example, byturning. A through-bore 46 is provided in receiving flange 45 anddisk-shaped region 44. The through-bore 46 is provided with an internalthread 47, which corresponds to a matching external thread 48 of pistonrod 30. Thus, second damper element 43 can be screwed onto piston rod30. A lock nut 49 fixes second damper element 43 with respect to pistonrod 30.

A damping cushion 50 is located between first damper element 40 andsecond damper element 43. The damping cushion 50 is a substantiallycircular torus of rectangular cross-section, as can be directly seenfrom FIG. 2. Damping cushion 50 can be manufactured, for example, from aplastic, rubber, or other materials having good damping characteristics.A pin 51 of piston rod 30 extends through second damper element 43 anddamping cushion 50 into a bore 52 of first damping element 40. The fitbetween pin 51 and bore 52 is selected such that pin 51 is supported inbore 52 in such a manner that pin 51 can freely move in an axialdirection. The cup-shaped first region 41 of first damping element 40wraps around disk-shaped region 44 of second damper element 43. For thispurpose, first region 41 has an undercut 53, which allows first damperelement 40 to be clipped over second damper element 43 during assembly.First damper element 40 is axially movable relative to second damperelement 43 against the restoring or damping force exerted by dampingcushion 50. In this context, after assembly undercut 53 forms a stopwhich prevents first damper element 40 from being pulled off the seconddamper element 43. All aforementioned components of damping element 38,in particular first damper element 40 and second damper element 43 arepreferably made of plastic.

Housing 15 includes a first housing part 54 on which are located a firsthousing flange 55 and a second housing flange 56. Housing 15 furtherincludes a cylinder sleeve 57 located within first housing part 54,mainly in the region of pressure chamber 19. Furthermore, housing 15includes a weld flange 58 which is connected to a flange socket 60 ofhousing 15 by a flange 59. Flange 59 and flange socket 60 can be joinedtogether by screwing, bonding, or welding, for example, by ultrasonicwelding. First housing part 54 and weld flange 58 are preferably made ofplastic and thus the welding, if used in this case, is plastic welding.Cylinder sleeve 57 is preferably made of metal. However, other materialpairs of the housing parts and sleeve 57, such as plastic—plastic, arealso conceivable. The inside diameter of cylinder sleeve 57 and theinside diameter of weld flange 58 correspond to the outside diameter ofpiston 16. At the end face of weld flange 58 on the side of the housing,there is located a secondary seal 61. This seal 61 is a peripheral sealwhich serves to seal the actually non-pressurized region from theenvironment.

Housing 15 is provided with a replenishing port 62 which is connected toa replenishing nozzle 64 by a replenishing flange 63. Replenishingnozzle 64 is connected to a replenishing reservoir via a supply line.

Between secondary seal 61 and primary seal 28, there remains areplenishing chamber 65. During operation of master cylinder 4, pressurechamber 19, replenishing chamber 65, replenishing port 62, andassociated parts are filled with a hydraulic fluid. The replenishingline, and thus also replenishing chamber 65, are essentially at ambientpressure. When master cylinder 4 is in the rear position, which is shownin FIG. 2, pressure chamber 19 is directly connected to replenishingchamber 65 via a so-called “breather clearance” between primary seal 28and cylinder bore or sleeve 57. In this manner, hydraulic fluid lost dueto leaks in the overall system or other losses can be replenishedautomatically.

FIG. 6 shows an enlarged detail of replenishing nozzle 64. Replenishingnozzle 64 is pressed into replenishing flange 63. On the side ofreplenishing nozzle 64 facing piston 16, there is arranged a projection67. As can be seen in FIGS. 2, 3 and 6, projection 67 extends beyond asubstantially cylindrical or truncated-cone-shaped slip socket 66, andso far into housing 15 that it reaches down to the level of cylindersleeve 57 in a radial direction with respect to the direction ofmovement of piston 16, and that it touches a contact surface 79 or thatit partially reaches in a radial direction behind cylinder sleeve 57.Cylinder sleeve 57 has a radially outwardly enlarged collar 80. Thus, itis sufficient for projection 67 to reach to inside diameter 83 of collar80 in a radial direction with respect to axis of rotation 82 of piston16, thus leaving a gap 81 between piston 16 and projection 67. Theposition of projection 67 with respect to longitudinal axis 84 of slipsocket 66 is on the side of slip socket 66 or replenishing nozzle 64facing away from pressure chamber 19. Projection 67 prevents cylindersleeve 57 from being pulled out of housing 15, especially duringtransport prior to the final assembly of master cylinder 4, i.e., whenpiston 16 is not yet installed. Moreover, projection 67 securesreplenishing nozzle 64 against rotation. Projection 67 is essentially aflat plate, or it is circularly curved to match the inside diameter ofreplenishing nozzle 64. When attempting to rotate replenishing nozzle64, projection 67 butts against cylinder sleeve 57 with one of its outeredges, preventing rotation. Located on replenishing nozzle 64 is a ring108 which limits the insertion depth of replenishing nozzle 64 intoreplenishing flange 63. Ring 108 can additionally be welded or bonded toreplenishing flange 63.

FIG. 3 shows master cylinder 4 in the end position, where it iscompletely pressed in. Here, many of the reference numerals were omittedfor the sake of clarity. It can be clearly seen that piston 16 andextension 20 fill virtually the entire pressure chamber 19, which is whyonly small amounts of hydraulic fluid need to be used.

To illustrate the spatial arrangement of the individual elements, FIG. 4shows the master cylinder according to the present invention in athree-dimensional representation. For the sake of simplicity, onlyhousing 15, piston rod 30, as well as damping element 38, first housingflange 55, second housing flange 56, and replenishing line 64 areprovided with reference numerals here.

An adapter 68 for connection of the line sections 11 or 12 is locatedlaterally on housing 15 in the front region of pressure chamber 19.

FIG. 5 shows adapter 68 in a section along line A-A in FIG. 3. Adapter68 includes a housing flange 69 in which is located a sleeve 70. Sleeve70 is preferably a metal sleeve. Housing flange 69 includes a steppedbore 71 having a first step 72 of a larger diameter and a second step 73of a smaller diameter. Sleeve 70 also has a first region 74 with anoutside diameter approximately equal to the inside diameter of firststep 72, as well as a second region 75 whose outside diameter isapproximately equal to the inside diameter of second step 73. An annularseal 76 is located between second region 75 and second step 73. Theannular seal can be, for example, a plastic seal or the like, whichswells upon contact with the hydraulic fluid. Alternatively, it ispossible to use other known seals. Preferably, second region 75 and,accordingly, second step 73 are approximately circular in cross-section.In contrast, first step 72 and, accordingly, first region 74 havecorresponding, polygonal cross-sections. For example, a rectangular,hexagonal or octagonal cross-section can be used here. The polygonalcross-section prevents rotation of sleeve 70 with respect to housingflange 69. First step 72 and second step 73 of stepped bore 71 can eachhave a circular inside diameter. In this case, sleeve 70 is pressed intostepped bore 71 with the polygonal sections, thereby creatingcorresponding, polygonal cross-sections of stepped bore 71. Insidediameter 78 of sleeve 70 is circular, and serves to receive, in knownmanner, a hydraulic connector of line section 12, which is then in fluidconnection with pressure chamber 19.

In known manner, housing flange 69 and sleeve 70 have a double groove 77(see FIG. 4 as well) to receive a clamping spring when connecting apressure-medium line.

FIG. 6 shows an enlarged detail of FIG. 2 in the region of nozzle 64,and FIG. 7 is an enlarged detail of the front region of the mastercylinder of FIG. 2.

FIG. 8 shows a damping device 2 in the form of a disk 91 a. This dampingdevice is inserted in the pressure-medium line and connected to linessections 11 and 12 by its bores 95 a and 96 a. As the vibration-carryingfluid flows through disk 91 a, it is positively guided, starting fromthe entry, for example, through bore 95 a, along annular grooves 93until it is passed on to the system through bore 96 a. Ridges 94alternate between ending at spline 92 and ending short of spline 92. Thedamping of the vibrations is accomplished over the groove path, whichconstitutes an extension of the path of the pressure medium.

FIG. 9 is a cross-section of disk 91 a, showing the profile thereof.Ridges 94 alternate with grooves 93.

FIG. 10 shows a different embodiment of a damping device 2. Here, alabyrinth body 91 b including a housing 97 (FIG. 11) and a cylinder,which is provided with bores extending in an axial direction and whichis sealed and closed with a cover 100, is inserted in one of linesections 11 or 12. This cover, in turn, is connected to the line systemvia bores 95 b and 96 b. This embodiment represents a further way ofextending the path of the pressure medium. Starting from the entry ofthe pressure medium, for example, through bore 95 b, the pressure mediumis positively guided in labyrinth body 91 b in the bores 101.

For purposes of illustration, FIG. 11 shows the labyrinth body 91 b incross-section.

FIG. 12 is a schematic representation of a damping device 91 with thecombination of a pulsation filter 91 c and a throttle 102, which, in theexemplary embodiment, is designed as a laminar throttle.

The different passageways of the fluid through the damping deviceaccording to FIG. 12 can be seen in FIG. 13. When pulsation filter 91 cis closed, the fluid flows only through throttle 102, which follows fromstep 1). When the fluid coming from the engine exceeds a certainpressure, a valve of pulsation filter 91 c opens as well, and the fluidflows through pulsation filter 91 c in the direction of the actuatingdevice, as shown in FIG. 13 2 a). The opposite case is obvious from 2b). That is, when the actuating device is actuated, the fluid flowsthrough throttle 102 and through a valve of pulsation filter 91 c.

LIST OF REFERENCE NUMERALS

-   1 hydraulic system-   2 pressure-limiting valve or damping element-   3 clutch release device-   4 master cylinder-   5 slave cylinder-   6 disengagement mechanism-   7 clutch-   8 internal combustion engine-   9 crankshaft-   10 transmission input shaft-   11 line section-   12 line section-   13 mechanical transmission means-   14 actuating member-   15 housing-   16 piston-   17 double arrow for the axial direction-   18 cylinder bore-   19 pressure chamber-   20 extension-   21 piston crown-   22 auxiliary chamber-   23 bottom-   24 biasing spring-   25 spring retainer-   26 enlarged portion-   27 annular groove-   28 primary seal-   29 rear region-   30 piston rod-   31 spherical segment-   32 spherical recess-   33 rear edge-   34 truncated cone-   35 ball head-   36 stop disk-   37 stop-   38 damping element-   39 connecting piece-   40 first damper element-   41 first region-   42 second region-   43 second damper element-   44 disk-shaped region-   45 receiving flange-   46 through-bore-   47 internal thread-   48 external thread-   49 lock nut-   50 damping cushion-   51 pin-   52 bore-   53 undercut-   54 first housing part-   55 first housing flange-   56 second housing flange-   57 cylinder sleeve-   58 weld flange-   59 flange-   60 flange socket-   61 secondary seal-   62 replenishing port-   63 replenishing flange-   64 replenishing nozzle-   65 replenishing chamber-   66 slip socket-   67 projection-   68 adapter-   69 housing flange-   70 sleeve-   71 stepped bore-   72 first step-   73 second step-   74 first region-   75 second region-   76 annular seal-   77 double groove-   78 inside diameter-   79 contact surface-   80 collar-   81 gap between piston 16 and projection 67-   82 axis of rotation of piston 16-   83 inside diameter-   84 longitudinal axis of the slip socket 66-   85 front end-   86 nose-   87 overlength-   88 end face-   89 seal-   90 breather port/groove-   91 damping element-   91 a disk-   91 b labyrinth body-   91 c pulsation filter-   92 spline-   93 annular groove-   94 ridges-   94 a grooves-   94 b walls-   95 a bore extending perpendicularly-   95 b bore extending perpendicularly-   96 a bore extending axially-   96 b bore extending axially-   97 housing-   98 cylinder-   99 seals-   100 cover-   101 bores-   102 laminar throttle-   108 ring

1. A hydraulic system comprising: a master cylinder having a housing, apiston axially movably disposed in the housing, and a piston rod, thepiston bounding a pressure chamber filled with a hydraulic fluid, thepiston upon actuation of the master cylinder being axially moved by thepiston rod to pressurize the hydraulic fluid; an actuating device formoving the piston rod, the piston rod extending past the housing in adirection of the actuating device; a connecting piece for directconnection to the actuating device; a slave cylinder; a pressure-mediumline connecting the master cylinder and slave cylinder; wherein thepiston rod connects to at least one damping element arranged between thepiston rod and the connecting piece, wherein the piston rod, the dampingelement and the connecting piece are axially aligned, the dampingelement including a damping cushion, a first damper element connected tothe connecting piece and a second damper element connected to the pistonrod; wherein the first damper element being axially movable relative tothe second damper element; the first damper element including acup-shaped section with an open end and the second damper elementincluding a disk shaped region closing the open end; the first damperelement having an undercut at the open end, the undercut allowing thefirst damper element to be clipped over the second damper element, theundercut forming a stop for the second damper element, wherein the firstdamper element includes the cup-shaped section encompassing the dampingcushion and a further region supporting the connecting piece, whereinthe piston rod has a pin which extends at least partially into a bore ofthe further region.
 2. A hydraulic system comprising: a master cylinderhaving a housing, a piston axially movably disposed in the housing, anda piston rod, the piston bounding a pressure chamber filled with ahydraulic fluid, the piston upon actuation of the master cylinder beingaxially moved by the piston rod to pressurize the hydraulic fluid; anactuating device for moving the piston rod, the piston rod extendingpast the housing in a direction of the actuating device; a connectingpiece for direct connection to the actuating device; a slave cylinder; apressure-medium line connecting the master cylinder and slave cylinder;wherein the piston rod connects to at least one damping element arrangedbetween the piston rod and the connecting piece, wherein the piston rod,the damping element and the connecting piece are axially aligned, thedamping element including a damping cushion, a first damper elementconnected to the connecting piece and a second damper element connectedto the piston rod; wherein the first damper element being axiallymovable relative to the second damper element; the first damper elementincluding a cup-shaped section with an open end and the second damperelement including a disk shaped region closing the open end; the firstdamper element having an undercut at the open end, the undercut allowingthe first damper element to be clipped over the second damper element,the undercut forming a stop for the second damper element, wherein thefirst damper element includes the cup-shaped section encompassing thedamping cushion and a further region supporting the connecting piece,wherein the piston rod has a pin which extends at least partially into abore of the further region, wherein the pin is arranged in the bore soas to be axially movable.
 3. A hydraulic system comprising: a mastercylinder having a housing, a piston axially movably disposed in thehousing, and a piston rod, the piston bounding a pressure chamber filledwith a hydraulic fluid, the piston upon actuation of the master cylinderbeing axially moved by the piston rod to pressurize the hydraulic fluid;an actuating device for moving the piston rod, the piston rod extendingpast the housing in a direction of the actuating device; a connectingpiece for direct connection to the actuating device; a slave cylinder; apressure-medium line connecting the master cylinder and slave cylinder;wherein the piston rod connects to at least one damping element arrangedbetween the piston rod and the connecting piece, wherein the piston rod,the damping element and the connecting piece are axially aligned, thedamping element including a damping cushion, a first damper elementconnected to the connecting piece and a second damper element connectedto the piston rod; wherein the first damper element being axiallymovable relative to the second damper element; the first damper elementincluding a cup-shaped section with an open end and the second damperelement including a disk shaped region closing the open end; the firstdamper element having an undercut at the open end, the undercut allowingthe first damper element to be clipped over the second damper element,the undercut forming a stop for the second damper element, wherein thedamping cushion is a circular torus of a rectangular cross-section.